Motor vehicles are commonly provided with speedometers which comprise a combination of instant speed and accumulated travel distance indications.
Prior art abounds with instant speed indicators, an example being that of Hayaski, et al. in U.S. Pat. No. 4,368,426.
An odometer providing electronic retention of accumulated travel distance is the subject of my present invention. Ordinarily motor vehicles accumulate travel mileage (or the metric equivalent in kilometers) on a plurality of numeral wheels which are reduction geared to the vehicle drive train to advance in relation to the preferred units of measurement. The widely used "Veeder Root" counter design particularly exemplifies a popular commercial embodiment of this kind of odometer accumulating display.
A train of pulse signals (binary transitions) may be produced by the vehicle drive train, with the interval between pulses being proportional to distance travelled. By way of example, the speed pulses in the mentioned Hayaski patent also provide distance travelled information which might be further processed, as by way of a succession of frequency dividers, etc. The divided down pulses appear as binary signals at the counter outputs which may then be decoded and displayed. While this approach provides an indication of travel distance, it is lacking commercial usefulness in that it does not provide for the permanent retention of mileage. The information is lost when power to the counters is removed (as with a dead vehicle battery, etc.). The counter outputs may also be stored in a supplementary resister which has a source of standby power, yet such storage is still merely semipermanent.
A practitioner of my instant invention will quickly realize that I now provide substantially permanent, irreversible and tamperproof digital storage of each travelled unit of distance, while using a minimum size memory for obtaining adequate storage.